The Raspberry Pi 5 PCIe HAT is designed to bring precision timing and advanced network functionality to the Raspberry Pi 5 platform. Leveraging the PCIe interface via an FPC connection, this HAT expands the Pi's capabilities by integrating a high-performance I226 Ethernet NIC, precise timing inputs and outputs via SMA connectors, and a GNSS module slot for global time synchronization. It's a powerful tool for building small form-factor PTP (Precision Time Protocol) clients, ideal for time-sensitive networking applications.
Order from the Tindie Page: https://www.tindie.com/products/timeappliances/timehat-i226-nic-with-pps-inout-for-rpi5/
The stock Linux igc driver has limitations that prevent proper PPS (Pulse Per Second) input and output on the I226 NIC. This patched driver fixes those issues and is packaged as a DKMS module for easy installation.
Choose the correct zip for your kernel version (uname -r):
| Kernel | Zip File |
|---|---|
| 6.6.x (RPi5 stable as of 4/2025) | intel-igc-ppsfix_rpi5_6_6.zip |
| 6.12.x (RPi5 previous, Intel OOT driver based) | intel-igc-ppsfix_rpi5_6_12.zip |
| 6.12.62 (RPi5 latest as of 3/9/2026, upstream source based) | intel-igc-ppsfix_rpi5_6.12.62.zip |
Problem: The I226 hardware triggers timestamps on both rising and falling edges. The stock driver requires PTP_STRICT_FLAGS with both edges enabled, making single-edge filtering impossible. GPS PPS signals are rising-edge only.
Fix: Bypasses the strict dual-edge requirement and forces rising-edge-only mode when enabling EXTTS. A GPIO-level workaround in the interrupt handler reads the actual pin state after each edge event and filters out the wrong edge, since the hardware doesn't natively support single-edge timestamping.
Problem: When requesting 1PPS output via testptp -p 1000000000, the kernel computes period/2 = 500000000 ns. The stock driver treats this as a "use frequency mode" case, producing a free-running 1Hz square wave that is not aligned to the PTP clock's second boundary.
Fix: Removes 500000000 from the frequency-mode condition, forcing 1PPS to use Target Time (TT) mode instead. In TT mode, the output toggles at each target time and re-arms in the interrupt handler, producing PPS pulses aligned to the PTP clock's top of second.
Problem: The I226's internal GPIO read has propagation delays that can cause the pin value to be read incorrectly immediately after an edge interrupt.
Fix: Adds a configurable microsecond delay before reading the GPIO pin state (edge_check_delay_us, default 20µs). Also adds an invertible check (edge_check_invert, default 0) since some I226 chips report the opposite GPIO level. Both parameters are tunable at runtime via sysfs without rebuilding the module.
Problem: The stock igc_adapter struct doesn't track which pins and flags are assigned to each EXTTS channel.
Fix: Adds ts0_pin, ts1_pin, ts0_flags, ts1_flags fields to the adapter struct, used by the GPIO edge filtering logic.
Install dependencies:
sudo apt install -y net-tools gcc vim dkms linuxptp raspberrypi-kernel-headersInstall testptp (used for testing PPS):
cd ~ && mkdir -p testptp && cd testptp
wget https://raw.githubusercontent.com/torvalds/linux/refs/heads/master/tools/testing/selftests/ptp/testptp.c
wget https://raw.githubusercontent.com/torvalds/linux/refs/heads/master/include/uapi/linux/ptp_clock.h
sudo cp ptp_clock.h /usr/include/linux/ptp_clock.h
gcc -Wall -lrt testptp.c -o testptp
sudo cp testptp /usr/bin/- Download and unzip the correct patch for your kernel:
cd ~
# For kernel 6.12.62 (RPi5 latest as of 3/9/2026):
wget https://github.com/Time-Appliances-Project/TimeHAT/raw/refs/heads/main/intel-igc-ppsfix_rpi5_6.12.62.zip
unzip intel-igc-ppsfix_rpi5_6.12.62.zip -d intel-igc-ppsfix_6_12
cd intel-igc-ppsfix_6_12- Register, build, and install the DKMS module:
sudo dkms add .
sudo dkms build --force igc -v 6.12.0-ppsfix.1
sudo dkms install --force igc -v 6.12.0-ppsfix.1- Back up the stock kernel module and replace it:
sudo cp /lib/modules/$(uname -r)/kernel/drivers/net/ethernet/intel/igc/igc.ko.xz \
/lib/modules/$(uname -r)/kernel/drivers/net/ethernet/intel/igc/igc.ko.xz.bak
sudo cp /lib/modules/$(uname -r)/updates/dkms/igc.ko.xz \
/lib/modules/$(uname -r)/kernel/drivers/net/ethernet/intel/igc/igc.ko.xz- Update module cache and initramfs:
sudo depmod -a
sudo update-initramfs -u -k $(uname -r)- Reboot:
sudo rebootIf you edit the source files and need to rebuild:
# Copy changed source to DKMS tree
sudo cp ~/intel-igc-ppsfix_6_12/src/igc_main.c /usr/src/igc-6.12.0-ppsfix.1/src/igc_main.c
# Rebuild and reinstall
sudo dkms build --force igc -v 6.12.0-ppsfix.1
sudo dkms install --force igc -v 6.12.0-ppsfix.1
# Reload without rebooting
sudo rmmod igc && sudo modprobe igc# Confirm DKMS module is loaded (should show /updates/dkms/ path)
modinfo igc | grep filename
# Check driver info
ethtool -i enp1s0Connect an SMA loopback cable between the two SMA connectors, then:
# Configure pin 0 as PPS output (perout), pin 1 as PPS input (extts)
sudo testptp -d /dev/ptp0 -L 0,2
sudo testptp -d /dev/ptp0 -L 1,1
# Start 1PPS output
sudo testptp -d /dev/ptp0 -p 1000000000
# Read 5 external timestamps (should show ~1.000000000s intervals)
sudo testptp -d /dev/ptp0 -e 5With a GPS PPS signal connected to an SMA input:
# Configure pin 2 as extts input
sudo testptp -d /dev/ptp0 -L 2,1
# Read timestamps (should show 1 event per second)
sudo testptp -d /dev/ptp0 -e 5Use ts2phc from the linuxptp package:
sudo ts2phc -c /dev/ptp0 -s generic --ts2phc.pin_index 2 -m -l 7These can be changed live without rebuilding:
| Parameter | Default | Description |
|---|---|---|
edge_check_delay_us |
20 | Microsecond delay before GPIO read for edge filtering |
edge_check_invert |
0 | Invert GPIO level check (0=normal, 1=inverted) |
# View current values
cat /sys/module/igc/parameters/edge_check_delay_us
cat /sys/module/igc/parameters/edge_check_invert
# Change at runtime
echo 50 | sudo tee /sys/module/igc/parameters/edge_check_delay_us
echo 1 | sudo tee /sys/module/igc/parameters/edge_check_invertTo make parameter overrides persistent across reboots:
echo "options igc edge_check_invert=1 edge_check_delay_us=20" | sudo tee /etc/modprobe.d/igc-ppsfix.conf- DKMS will automatically rebuild the module when the kernel is updated (
AUTOINSTALL=yesindkms.conf). - After a kernel update, you may need to re-run the stock module replacement (step 3) and
update-initramfs. - The patched module is built from the upstream Linux 6.12 igc source with PPS fixes applied on top.
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